Scintillator-based radiation therapy quality assurance

ABSTRACT

Systems, methods, and computer software are disclosed for determining a shape of a radiation field generated by a radiation delivery system through the use of a scintillator and a camera that is configured to acquire images of light emitted by the scintillator during delivery of a radiation beam. A support structure may be mounted to the radiation delivery system and the scintillator and camera may be fixed to the support structure such that the scintillator is not perpendicular to the axis of the radiation beam. An edge detection algorithm may be applied to radiation patterns present in the camera images in order to determine the location of an edge of a leaf of a multi-leaf collimator.

RELATED APPLICATION(S)

This application is a continuation of and claims priority to and thebenefit of U.S. patent application Ser. No. 16/925,205, filed Jul. 9,2020, titled “Scintillator-Based Radiation Therapy Quality Assurance,”which claims priority to and benefit of U.S. Provisional Application No.62/872,646, filed Jul. 10, 2019, titled “Scintillator-Based RadiationTherapy Quality Assurance,” which is hereby incorporated by reference.

DESCRIPTION OF THE RELATED ART

Radiation therapy can be utilized in the treatment of diseases, forexample, by delivering a dose of radiation to kill or to inhibit growthof a cancerous tumor. Devices to deliver radiation therapy can include,for example, radioisotopes, heavy ion accelerators and linearaccelerators that generate a photon beam directed at a tumor site. Toirradiate a tumor while minimizing exposure to nearby healthy tissues, aradiation beam can be shaped by a collimating device, for example, amultileaf collimator (MLC). Multileaf collimators include a number ofmovable leaves that can be positioned to create a shaped aperture (e.g.,shaped the same as the tumor, from the vantage point of the radiationbeam).

Radiation therapy quality assurance can be performed to verify theproper operation of one or more components of a radiation therapydelivery system, for example, verifying the positioning of MLC leaves.In certain circumstances, radiation detectors such as scintillators maybe used in performing such quality assurance. Scintillators emit lightin response to being struck by radiation and the emitted light can bedetected and analyzed to assist in determining whether radiation hasbeen delivered properly.

SUMMARY

Systems, computer program products, and methods are disclosed fordetermining a shape of a radiation field generated by a radiationdelivery system that includes a radiation source configured to deliver aradiation beam. An implementation of the system that determines theshape of the radiation field includes a scintillator and a cameraconfigured to acquire images of light emitted by the scintillator duringdelivery of the radiation beam. The system also includes a supportstructure configured to be mounted to the radiation delivery system. Thescintillator and the camera are fixed to the support structure such thatwhen the support structure is mounted to the radiation delivery system,the scintillator is not perpendicular to an axis of the radiation beam.

In some implementations, the system can be configured to be locatedbetween the radiation source and a patient couch.

In other implementations, the scintillator can include a planar sheet ofscintillating material. The scintillator can be transparent, allowingformation of a pattern at a target location corresponding to the shapeof a collimator aperture when a light source shines light through thecollimator aperture onto the scintillator.

In yet other implementations the scintillator and the camera can befixed to the support structure in a manner that sets a specific desiredgeometric relationship between the scintillator and the camera. Forexample, the scintillator can be at an angle of between 80 to 89 degreesor between 91 and 110 degrees relative to the axis of the radiation beamwhen the support structure is mounted to the radiation delivery system.Also, the support structure can be configured to allow mounting in anaccessory tray disposed between the radiation source and a patientcouch.

In another implementation, the system includes a scintillator mounted tothe radiation delivery system such that the scintillator substantiallyfollows a contour of a bore of the radiation delivery system. The systemincludes cameras configured to acquire images of light emitted by thescintillator during delivery of the radiation beam. The cameras areconfigured to be mounted an angle of greater than 0 and less than 10degrees relative to the scintillator.

In some implementations, the bore can be part of an MRI-guidedradiotherapy system. The scintillator can be a curved sheet ofscintillating material or planar sheets of scintillating material. Atleast a portion of the scintillator can remain perpendicular to the axisof the radiation beam when the radiation source is controlled to movearound the bore.

Any of the disclosed systems can also include software that performsvarious operations. Such operations can include applying an edgedetection algorithm to a radiation pattern present in the images. Theedge detection algorithm can determine an edge of the radiation patterncorresponding to a leaf of a multi-leaf collimator. A leaf position canbe determined based on a location of the determined edge.

In some implementations, the operations can include comparing the leafposition during delivery of the radiation beam with a planned leafposition, for example when utilized in radiation therapy qualityassurance. A fluence map can also be calculated based at least on theleaf position and beam output data obtained from the radiation therapysystem and a dose can be calculated at a target location based at leaston the fluence map and a patient image obtained from an imaging system.

Implementations of the current subject matter can include, but are notlimited to, methods consistent with the descriptions provided herein aswell as articles that comprise a tangibly embodied machine-readablemedium operable to cause one or more machines (e.g., computers, etc.) toresult in operations implementing one or more of the described features.Similarly, computer systems are also contemplated that may include oneor more processors and one or more memories coupled to the one or moreprocessors. A memory, which can include a computer-readable storagemedium, may include, encode, store, or the like, one or more programsthat cause one or more processors to perform one or more of theoperations described herein. Computer implemented methods consistentwith one or more implementations of the current subject matter can beimplemented by one or more data processors residing in a singlecomputing system or across multiple computing systems. Such multiplecomputing systems can be connected and can exchange data and/or commandsor other instructions or the like via one or more connections, includingbut not limited to a connection over a network (e.g., the internet, awireless wide area network, a local area network, a wide area network, awired network, or the like), via a direct connection between one or moreof the multiple computing systems, etc.

The details of one or more variations of the subject matter describedherein are set forth in the accompanying drawings and the descriptionbelow. Other features and advantages of the subject matter describedherein will be apparent from the description and drawings, and from theclaims. While certain features of the currently disclosed subject matterare described for illustrative purposes in relation to particularimplementations, it should be readily understood that such features arenot intended to be limiting. The claims that follow this disclosure areintended to define the scope of the protected subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, show certain aspects of the subject matterdisclosed herein and, together with the description, help explain someof the principles associated with the disclosed implementations. In thedrawings,

FIG. 1A is a diagram illustrating a perspective view of a simplifiedexemplary radiation delivery system in accordance with certain aspectsof the present disclosure,

FIG. 1B is a diagram illustrating a side-sectional view of thesimplified exemplary radiation delivery system of FIG. 1A in accordancewith certain aspects of the present disclosure,

FIG. 2 is a diagram illustrating a perspective view of a simplifiedexemplary multileaf collimator shaping a radiation field in accordancewith certain aspects of the present disclosure,

FIG. 3 is a diagram illustrating views of a simplified exemplaryradiation pattern at a scintillator in accordance with certain aspectsof the present disclosure,

FIG. 4 is a diagram illustrating an end-perspective view of a simplifiedexemplary scintillator fixed in an orientation that is not perpendicularto the radiation beam axis in accordance with certain aspects of thepresent disclosure,

FIG. 5A is a diagram illustrating a perspective view of a simplifiedexemplary scintillator and camera fixed in a supporting structure inaccordance with certain aspects of the present disclosure,

FIG. 5B is a diagram illustrating a perspective view of a simplifiedexemplary scintillator and camera fixed in a supporting structure thatis open on a top and bottom portion in accordance with certain aspectsof the present disclosure,

FIG. 6 is a diagram illustrating a perspective view of a simplifiedexemplary combined radiotherapy and medical imaging system in accordancewith certain aspects of the present disclosure,

FIG. 7 is a diagram illustrating a side-sectional view of the simplifiedexemplary combined radiotherapy and medical imaging system of FIG. 6 inaccordance with certain aspects of the present disclosure,

FIG. 8 is a diagram illustrating an end-perspective view down the boreof the simplified exemplary combined radiotherapy and medical imagingsystem of FIG. 6, showing exemplary scintillators and cameras inaccordance with certain aspects of the present disclosure,

FIG. 9 is a diagram illustrating an exemplary method of determining leafpositions of a multileaf collimator in accordance with certain aspectsof the present disclosure,

FIG. 10 is a diagram illustrating an exemplary geometric method ofdetermining a leaf position of a multileaf collimator from a radiationpattern in accordance with certain aspects of the present disclosure.

DETAILED DESCRIPTION

Radiation therapy quality assurance is a field that includes, amongother things, determining whether a radiation delivery system isfunctioning properly and providing the prescribed radiation dose to apatient as detailed in a radiation therapy treatment plan. While manyradiation delivery systems include their own functionality fordisplaying output and diagnostic metrics, radiation therapy qualityassurance products can obtain independent measurements of what theradiation delivery system is providing.

As used herein, the term “radiation delivery system” can include variouscomponents needed to generate, direct and control a radiation therapybeam. For example, a radiation therapy system can include a radiationsource (e.g. a linear accelerator, particle beam source, etc.), a gantry(fixed or rotating), a collimator (to shape the radiation reaching thepatient), imaging equipment (to image prior to or during therapy), andthe like.

As part of quality assurance, the operation of various components of theradiation delivery system can be independently assessed. Examples ofsuch operations can include, for example, verifying the output of theradiation source, the position of a rotating gantry, the configurationof a multileaf collimator (e.g., determining its leaf positions), etc.The present disclosure describes, among other things, systems, software,and methods for determining collimator configurations based on theanalysis of radiation patterns that emerge after a radiation beam passesthrough the collimator.

FIGS. 1A and 1B depict an exemplary radiation delivery system 100. Thisexemplary system is an open (or “C-arm”) type system that includes alinear accelerator (e.g., element 110 in FIG. 1B) working with an RFsource 150, a multileaf collimator 120, and a rotatable gantry 130. Inthis exemplary system, the linear accelerator and multileaf collimatorare mounted within the rotatable gantry to allow radiation beam 160 tobe delivered along beam axis 170 to a patient 10 at multiple angles.FIG. 1A also depicts an accessory tray 140 that can permit the mountingor positioning of hardware or devices between the radiation source andthe patient. As described further herein, the technologies of thepresent disclosure can be used with radiation delivery systems such asthe exemplary system depicted in FIGS. 1A and 1B, as well as with othertypes of radiotherapy systems.

When performing radiation therapy quality assurance, one element of theradiation therapy device that can be assessed is the multileafcollimator (e.g., through verifying the collimator's leaf positions).One method for MLC configuration verification may involve examining theshape of the radiation field delivered to the patient by a radiationdelivery system 100 including a radiation source (e.g., linearaccelerator 110) configured to deliver a radiation beam 160. As shown inthe simplified example of FIG. 2, a radiation field 210 can be shaped byblocking some portions with the leaves 220 of a multileaf collimator 120to form an aperture 230. The portion of the radiation field that passesthrough the aperture will then proceed to the patient to deliver a doseof radiation in the desired shape. As used herein, the term “radiationfield” can refer to radiation before or after being shaped by acollimator.

Scintillating materials may be used to determine the shape of aradiation field emerging from a multileaf collimator. “Determining theshape” can include determining the overall shape, determining particularMLC leaf positions (which provides information regarding the shape),etc.

“Scintillators,” as discussed herein, are understood to include anymaterial that, when hit by radiation, emit radiation (e.g., particle orphoton) that can be detected (for example, by a camera). Scintillatorsinclude materials that absorb incoming radiation and then re-emit aportion of the absorbed energy in the form of light. It should be notedthat when the term “light” is used herein, it is intended to includeradiation within, or not within, the visible spectrum (for example,scintillators that emit infrared or other types of radiation arecontemplated). Examples of scintillators can include plasticscintillators (such as Li6 plastic scintillators or polyethylenenaphthalate), luminophores, crystal scintillators, phosphorescentmaterials, etc. As used herein, a “camera” can be any device that candetect radiation (e.g., light) coming from a scintillator. Examples ofcameras can include CCD cameras, photodiodes, photomultiplier tubes,etc.

The top portion of FIG. 3 illustrates a simplified example of ascintillator 310 receiving a radiation beam 160 from radiation deliverysystem 110, after it passes through a multileaf collimator 120.

The lower portion of FIG. 3 illustrates a simplified example of a systemfor detecting a radiation pattern 320 from scintillator 310 using acamera 330. The radiation pattern 320 is related to the shape of theaperture formed by the multileaf collimator (as used herein, “radiationpattern” refers to the pattern present at the scintillator as it emitsradiation/light after exposure to a radiation field).

Analysis of the images or signals acquired by the camera from thescintillator's radiation patterns can provide estimates of leafpositions of the multileaf collimator, independent of leaf positioninformation that may be provided by the radiation delivery systemitself.

The present disclosure describes, among other things, technologiesutilizing scintillators to verify collimator leaf positions. However,contrary to what is common in the art, the present disclosure describescertain embodiments that utilize a scintillator that is tilted, so as tonot be perpendicular to the axis of the radiation beam. Also contrary tothe art, certain embodiments disclose a scintillator system with a veryshallow angle between the camera and the scintillator. For example,disclosed systems may be configured such that the angle between a planarscintillator and the camera's line of sight is less than 10 degrees.

One implementation of the disclosed technology for determining at leasta portion of a shape of a radiation field is depicted in FIG. 4. Thefigure illustrates a simplified representation of a radiation source 402and a series of collimators (an X-axis jaw 410, a Y-axis jaw 420, and amultileaf collimator 120). Also illustrated is a patient 10 lying on acouch 430 such that the patient is hit by radiation beam 160 after itspasses through the collimators. An accessory tray 140 is also depictedbetween the collimators and the patient couch.

The exemplary system of FIG. 4 can also include a scintillator 440 and acamera 450 configured to acquire images of light emitted by thescintillator during delivery of the radiation beam. As shown in FIG. 4,the scintillator and camera system can be configured to be locatedbetween the radiation source and a patient couch, thus functioning as anentrance detector.

It is contemplated that scintillator 440 may include a planar sheet ofscintillating material or may include a curved sheet of scintillatingmaterial that may, for example, be oriented to have its convex surfacefacing toward the camera. In some embodiments, scintillator 440 may besized to be large enough to cover the largest radiation field theradiation delivery system can deliver (at the location of thescintillator). In other embodiments, scintillator 440 may be morecompact and may be smaller than the largest radiation field the systemcan deliver at the location of the scintillator, yet still sufficientfor performing some measure of quality assurance.

As illustrated in FIG. 5A, scintillator 440 and camera 450 can be fixedin a support structure 510. The support structure 510 may then beconfigured to be mounted to a radiation delivery system so that thescintillator will be struck by the radiation treatment beam.

The scintillator and camera are preferably fixed to the supportstructure in a manner that sets a specific desired geometricrelationship between the scintillator and camera. The exemplaryembodiment depicted in FIG. 5A illustrates a simplified framework wherethe scintillator is located within the support structure and the camerais located and configured to view one side of the scintillator (e.g.,its bottom surface). It is contemplated, however, that the camera may beplaced in a position to view the top surface of the scintillator or thatmore than one camera may be used.

In some embodiments, the scintillator and camera can be fixed to thesupport structure so that when the support structure is mounted to theradiation delivery system, the scintillator is not perpendicular to anaxis of the radiation beam. FIG. 4 illustrates such an example of ascintillator 440 not being perpendicular to the axis 170 of radiationbeam 160. When referring herein to a scintillator being oriented so thatit is not perpendicular to an axis of the radiation beam, such refers toan orientation that is purposefully not perpendicular (i.e., as opposedto an orientation that may slightly deviate from an intendedperpendicular positioning).

Some embodiments may have the scintillator fixed to the supportstructure so that the scintillator will be at an angle of between 80 to89 degrees or between 91 and 110 degrees relative to the axis of theradiation beam when the support structure is mounted to the radiationdelivery system. In other embodiments, the scintillator can be at anangle of between 84 and 88 degrees or between 92 and 96 degrees relativeto the axis of the radiation beam when the support structure is mountedto the radiation delivery system. While the exemplary embodimentdepicted in FIG. 4 shows a tilt in the Y direction, it is contemplatedthat a similar tilt could be implemented in the X direction or in boththe X and Y directions.

In some embodiments, such as the one depicted in FIG. 5A, camera 450 andscintillator 440 can be fixed to support structure locations thatmaximize the angle between the camera and the scintillator. In suchexamples, the camera may be at one end of the support structure, asdepicted, or may be in a corner of the support structure, or may even belocated outside the perimeter of the support structure. Such embodimentscan be beneficial in that the resolution of the radiation pattern imagedby the camera can be increased as compared to smaller angles where theradiation pattern is viewed more edge-on.

The design of the support structure can be substantially open aboveand/or below the scintillator to reduce or eliminate material that mayattenuate the radiation therapy beam. Alternatively, the scintillatorand the camera can be substantially enclosed by the support structure(for example, to prevent dust from accumulating on the scintillator orto protect it from damage or scratching). In such embodiments, the topportion and/or bottom portion of the support structure may be designedto provide only minimal attenuation of a radiation beam. For example,the top and/or bottom portion may be a layer of thin plastic or glassthat causes only slight attenuation of the radiation beam.

The example depicted in FIG. 5A can represent a support structure 510that substantially encloses the scintillator (i.e., is closed on allsides), but FIG. 5A is also intended to depict an example where thesupport structure 510 is merely a frame for mounting the scintillatorand camera—with all the sides and the top/bottom being open.

FIG. 5B Illustrates another exemplary embodiment in which the topportion and bottom portion of support structure 520 are open to allowlight or other radiation unobstructed access to/through thescintillator, but where the support structure 520 also includes closedstructural portions on its sides.

The present disclosure contemplates support structures that areconstructed to include any combination of open or closed ortransparent/translucent top, bottom or side materials.

Some embodiments of the present disclosure can enable the use of avisible light source (e.g., a tungsten or any sort of atomic lamp, or awhite light source) to check the shape of a collimator aperture whilethe scintillator/support structure is in place. In such embodiments, thesupport structure can include translucent or transparent portions, whichmay be, for example, the top portion, bottom portion, or any portion(s)that form the sides of the support structure. It is contemplated thatany combination of portions of the support structure may be translucentor transparent. Similarly, the scintillator may also be translucent ortransparent. Such translucent or transparent support structure portionsand/or scintillators can allow formation of a pattern at a targetlocation (e.g., at the isoplane) corresponding to the shape of acollimator aperture when a light source shines light through thecollimator aperture onto the scintillator and/or supporting structureportion. The present disclosure contemplates that any embodiments herein(not just planar scintillator embodiments) can incorporate transparentor translucent support structure portions and/or scintillators.

As used herein, the term “transparent” means that light corresponding tothe shape of the collimator aperture is able to pass through withoutsignificant distortion, resulting in a pattern that can be accuratelyrelated to the shape of the collimator aperture. Similarly, as usedherein, the term “translucent” means that light is able to pass, butthere may be some distortion or dimming of the light and the resultingpattern corresponding to the shape of the collimator aperture. Inembodiments where a translucent material is used, it is contemplatedthat degree of distortion will not be prohibitive of providing a patternthat can be utilized in radiation therapy quality assurance fordetermining the shape of a collimator aperture. Also, it is contemplatedthat the transparent or translucent material described herein can haveany degree of attenuation of light. For example, a transparentscintillator may attenuate 50% of light but still allow a sharp (thoughdimmer) pattern to be formed at the target location. According to thetype of application desired, translucent or transparent scintillatorscan have a polyvinyltoluene base, optionally including some fraction oflead (e.g., approximately 2%—appropriate for x-ray dosimetry), etc.

In some embodiments, the support structure can be configured to bemounted to the radiation delivery system at an accessory tray disposedbetween the radiation source and a patient couch. For example, a linearaccelerator may have an accessory tray or slot into which the supportstructure may be mounted. It thus contemplated herein that whenreference is made to a support structure being “configured to bemounted,” this can include, for example, being configured in a way to beremovably mounted (e.g., structurally designed to slide into anaccessory tray slot or specifically sized to fit within the tray).Support structures herein are also contemplated to be configured to bemounted by virtue of more permanent structures such as the provision ofscrew holes or other fastening accessories to aid in mounting to aparticular portion of a radiation delivery system.

In certain embodiments, the scintillator(s) and camera(s) can be fixedto the support structure in a manner so that the whole assembly fitsentirely within an accessory tray. The support structure mounting, inconjunction with specific fixation therein of the scintillator andcamera can result in a tilted scintillator orientation with regard tothe axis of the radiation beam. For example, mounting the supportstructure into a linac accessory tray that is perpendicular to the axisof the radiation beam, when the scintillator is fixed at an angle withinthe supporting structure, results in the scintillator being tilted withregard to the axis of the radiation beam.

In contrast to the scintillator/camera systems described above for aC-arm type radiation delivery system, the present disclosurecontemplates alternative embodiments for implementation with radiationdelivery systems having a bore, for example, a radiation delivery systemcombined with an imaging system such as an MRI. FIG. 6 shows asimplified example of such a system 600 that includes first and secondmagnet housings 602 and 604 separated by gap region 612. A radiationsource 606 can be mounted to a gantry adjacent to or in a gap region612. A patient can be positioned on couch 614 inside bore 616 of themagnet so that the gantry can cause rotation of radiation source 606around the patient.

FIG. 7 depicts a cross-sectional view of the exemplary system shown inFIG. 6. Such a system can be used to image a target region 702 (e.g., avolume and/or area within a patient), while radiation source 606 emitsradiation 704 for patient treatment. Also shown is a multileafcollimator 710 for shaping the radiation beam directed toward thepatient. The system illustrated in FIGS. 6 and 7 is only one example ofa radiotherapy system having a bore that is compatible with embodimentsof the present disclosure. Implementations of the technologies hereinmay also be used with other types of radiotherapy systems that include apatient bore.

Scintillators that are shaped or configured for radiotherapy systemshaving a bore may be utilized in certain implementations. For example,as shown FIG. 8, scintillator 810 can be mounted to radiation deliverysystem 600 such that scintillator 810 substantially follows the contourof a bore 616 of a radiation delivery system 600. As noted above withregard to FIGS. 6 and 7, the bore may be part of an MRI-guidedradiotherapy system. “Substantially following the contour of a bore” isunderstood to include, for example, following the internal surface ofthe bore or having generally the same contour as the bore but a slightlylarger or smaller diameter, etc.

The scintillator may be a continuous sheet of scintillating material ormay be comprised of multiple sheets. The example of FIG. 8 illustratesan exemplary scintillator having multiple curved sheets of scintillatingmaterial, specifically, eight curved sheets, each covering 45 degrees ofthe bore. In other implementations, the scintillator may be made up of anumber of planar sheets of scintillating material. For example, theconfiguration shown in FIG. 8 could instead be comprised of eight planarsheets, meeting at their edges. It is contemplated that any number ofcurved or planar sheets can be implemented, in any feasible combination,to cover a desired portion of the bore and they can be located at anyradial distance from the axis of the bore.

While the scintillator can extend around the entire circumference of thebore, it is not essential that it do so. For example, the scintillatorcan cover any degree or angular measure of the bore (e.g., 270 degrees,180 degrees, 90 degrees, 45 degrees, etc.) and may be constituted of anynumber of sheets (e.g., ten sheets covering 27 degrees each, 18 sheetscovering 10 degrees each, etc.).

As described in further detail herein, mounting the scintillator to theradiation delivery system may include, for example: mounting thescintillator directly to a portion of the radiation delivery system suchas the gantry, the linac, the MLC, etc.; mounting the scintillator tothe bore of an imaging system associated with the radiation deliverysystem (e.g., an MRI for an MRI-guided radiation therapy system); and,mounting the scintillator indirectly, for example, mounting thescintillator to a supporting structure that can in turn be mounted toportions of the overall system (e.g., RT device, MRI, etc.).

In some embodiments, the scintillator can be mounted so it is at anangle to the radiation beam or the scintillator can be mounted so thatat least one portion of the scintillator remains perpendicular to axis830 of the radiation beam when the radiation source 606 is controlled tomove around the bore. For example, in instances where the radiation beamaxis 830 is radial and the scintillator is curved to be concentric withthe bore, at least one portion of the scintillator (e.g., where axis 830intersects the scintillator) would be perpendicular to axis 830.

One or more cameras configured to acquire images of light emitted by thescintillator during delivery of the radiation beam can be utilized.Similar to the previously-described embodiments, these may be mounted soas to have a shallow angle between the scintillator and the camera. Forexample, the cameras can be configured to be mounted at an angle ofgreater than 0 and less than 10 degrees relative to the scintillator. Inother embodiments, the cameras may be mounted to result in angles of10-20, 20-30, 30-40, 40-50 or 50-60 degrees between the scintillator andthe line of sight of the camera.

Cameras can be placed on the bore at various locations so they are ableto view at least a portion of the scintillator. The cameras can be smallso as to provide minimal intrusion into the inner volume of the borewhere the patient is located. As shown in the example of FIG. 8, each ofthe scintillator sections or sheets may have a corresponding camera witha field of view covering it (shown approximately by the dotted lines).The number and disposition of the cameras and their fields of view inFIG. 8 are examples only and other configurations are contemplated. Forexample, the fields of view can cover only a portion of a section ratherthan an entire section, the cameras can be located at any axial locationalong the bore, and they can be on either side of the scintillator.

In some embodiments, a support structure can be configured to be mountedto the bore, and the one or more cameras can be fixed to the supportstructure. In the present example, a support structure configured to bemounted to the bore may include a cylindrical framework that generallyconforms to the shape of the bore, such that the supporting structurehaving the cameras can be inserted or installed in the bore, without theneed to mount individual cameras to the bore structure itself. In suchembodiments, and other embodiments, such as those described above withreference to FIG. 8, the cameras can be oriented to view respectiveportions of the scintillator adjacent to the cameras. Here, thescintillator “adjacent the camera” means the scintillator can be locatedat least partially at the same angular location as the camera. Inaddition to mounting cameras on such a support structure, otherembodiments can include having the scintillator also mounted to thesupport structure. Such embodiments can allow for the entire assembly ofscintillators and cameras to be inserted or mounted to the bore as aunit, rather than as individual components.

Methods and software that enable the determination of MLC leaf positionsare disclosed herein. Leaf positions can be reflected in scintillatorradiation patterns imaged by one or more cameras, as described above. Inone embodiment, leaf position determination can be facilitated byanalyzing the edges of radiation patterns. As used herein, “radiationpattern” means the image of (or data representing the image of)scintillator light emitted due to interaction between the scintillatorand a radiation beam.

As illustrated by the example in FIG. 9, computer software can performoperations to determine edges of a radiation pattern. For example, at910, using the image data acquired from the camera(s), an edge detectionalgorithm (e.g., a Canny edge detection algorithm) can be applied to aradiation pattern present in the images. The edge detection algorithmcan determine at least one edge of the radiation pattern correspondingto a leaf of a multi-leaf collimator. From this, at 1020, a leafposition can be determined based at least on a location of thedetermined edge. Following this determination, it is possible to compareleaf positions during delivery of the radiation beam with planned leafpositions (e.g., as dictated by a radiation therapy plan and/or detailedin system log files). The comparison can thus be utilized in radiationtherapy quality assurance.

The process of determining leaf positions can then include, for example,compensating for image distortion caused by (or inherently present in) agiven camera or camera system. For example, lens aberrations, and cameraplacement with respect to the scintillator can be accounted for. Onemethod of accounting for optical effects from the camera system caninclude performing a calibration procedure with a well-known patternthat allows for a mapping of points in the image acquired by the camerato real positions in the object plane (e.g., the plane of a planarscintillator sheet). This correction/mapping can be performed for anynumber of opposing leaves of the MLC.

As part of radiation therapy quality assurance, it can be desired todetermine leaf positions at a plane through the isocenter. One methodfor doing so can include determining the effective size of an openingbetween collimator leaves at a plane parallel to the isocenter plane.Then, the effective MLC leaf positions at the isocenter plane can bedetermined based on the effective size, when geometrically extended tothe isocenter plane.

An exemplary arrangement of a simplified system used for the abovedetermination is illustrated in FIG. 10. Here, an example of a tiltedscintillator 1010 is shown with a camera 1020 imaging the scintillator1010. The radiation from radiation source 1005 passing through the MLC1025 results in a radiation pattern at the scintillator. The shape ofthe radiation pattern is a length (length_(screen)) 1030 thatcorresponds to the size of the opening between MLC leaves (which can bedirectly related to the position of the MLC leaves). One exemplaryformula for determining the length (length_(pp)) 1040 at on a planeparallel 1050 to the isocenter plane 1092 can be expressed as shown inEq. 1, below.

$\begin{matrix}{{{length}_{pp} = {\sqrt{{length}_{screen}^{2} - {height}^{2}} + \frac{x}{\left( {d_{1} + {height}} \right)}}}{{length}_{pp} = {\sqrt{{length}_{screen}^{2} - {height}^{2}} + {{height}{\frac{x}{\left( {d_{1} + {height}} \right)}.}}}}} & (1)\end{matrix}$

In Eq. 1, the height is the height 1060 of the radiation pattern asmeasured in the vertical direction (or parallel to the beam axis). X isthe X-coordinate 1070 of the right edge of the radiation pattern. d1(element 1080) is the height from the radiation source to the planeparallel to the isocenter plane. The expanded view on the right side ofFIG. 10 illustrates that length_(pp) 1040 can be found by accounting forthe vertical projection 1042 of the radiation pattern to the planeparallel 1050. Once length_(pp) is found the length (length_(iso)) 1090at the isocenter plane 1092 can be determined according to the followingrelation:

$\begin{matrix}{{length}_{iso} = {\frac{d_{2}}{d_{1}}{{length}_{pp}.}}} & (2)\end{matrix}$

In Eq. 2, d₂ (element 1095) is the distance from the radiation source tothe isocenter plane 1092. The above description and solution of thesimplified geometrical arrangement of the scintillator and camera systemshould not be considered limiting or exclusive of other solutions thatmay be implemented for embodiments described herein.

The methods and operations described herein can further enable thedetermination of fluence maps at the isocenter plane, which can beuseful for performing radiation therapy quality assurance. For example,the present disclosure contemplates software that can perform operationsthat include calculating a fluence map based at least on the leafpositions determined using the scintillator and also on beam output dataobtained from the radiation therapy system. Furthermore, operations suchas calculating a dose at a target location based at least on the fluencemap and a patient image obtained from an imaging system may also beperformed.

In the following, further features, characteristics, and exemplarytechnical solutions of the present disclosure will be described in termsof items that may be optionally claimed in any combination:

Item 1: A system for determining at least a portion of a shape of aradiation field generated by a radiation delivery system that includes aradiation source configured to deliver a radiation beam, the systemcomprising: a scintillator; a camera configured to acquire images oflight emitted by the scintillator during delivery of the radiation beam;and a support structure configured to be mounted to the radiationdelivery system, the scintillator and the camera fixed to the supportstructure such that when the support structure is mounted to theradiation delivery system, the scintillator is not perpendicular to anaxis of the radiation beam.

Item 2: The system of any one of the preceding items, wherein the systemis configured to be located between the radiation source and a patientcouch.

Item 3: The system of any one of the preceding items, wherein thescintillator includes a planar sheet of scintillating material.

Item 4: The system of any one of the preceding items, wherein thescintillator includes a curved sheet of scintillating material and thecurved sheet is oriented to have its convex surface oriented so as to befacing toward the camera.

Item 5: The system of any one of the preceding items, wherein thescintillator has a size large enough to cover the largest radiationfield that the radiation delivery system can deliver at the location ofthe scintillator.

Item 6: The system of any one of the preceding items, wherein thescintillator is transparent, the scintillator allowing formation of apattern at a target location corresponding to the shape of a collimatoraperture when a light source shines light through the collimatoraperture onto the scintillator.

Item 7: The system of any one of the preceding items, wherein thescintillator and the camera are fixed to the support structure in amanner that sets a specific desired geometric relationship between thescintillator and the camera.

Item 8: The system of any one of the preceding items, wherein thescintillator is fixed to the support structure so that the scintillatorwill be at an angle of between 80 to 89 degrees or between 91 and 110degrees relative to the axis of the radiation beam when the supportstructure is mounted to the radiation delivery system.

Item 9: The system of any one of the preceding items, wherein thescintillator is fixed to the support structure so that the scintillatorwill be at an angle of between 84 and 88 degrees or between 92 and 96degrees relative to the axis of the radiation beam when the supportstructure is mounted to the radiation delivery system.

Item 10: The system of any one of the preceding items, wherein thecamera and the scintillator are fixed to the support structure locationsthat maximize the angle between the camera and the scintillator.

Item 11: The system of any one of the preceding items, wherein thesupport structure is configured to allow mounting in an accessory traydisposed between the radiation source and a patient couch.

Item 12: The system of any one of the preceding items, wherein thesupport structure has a top portion and a bottom portion that is open.

Item 13: The system of any one of the preceding items, wherein thescintillator and the camera are substantially enclosed by the supportstructure, and the support structure includes a top portion and a bottomportion that provide only minimal attenuation of the radiation beam.

Item 14: A system for determining at least a portion of the shape of aradiation field generated by a radiation delivery system that includes aradiation source configured to deliver a radiation beam, systemcomprising: a scintillator mounted to the radiation delivery system suchthat the scintillator substantially follows a contour of a bore of theradiation delivery system; and one or more cameras configured to acquireimages of light emitted by the scintillator during delivery of theradiation beam, the one or more cameras configured to be mounted anangle of greater than 0 and less than 10 degrees relative to thescintillator.

Item 15: The system of any one of the preceding items, wherein thescintillator is a curved sheet of scintillating material.

Item 16: The system of any one of the preceding items, wherein thescintillator comprises a plurality of planar sheets of scintillatingmaterial.

Item 17: The system of any one of the preceding items, wherein at leastone portion of the scintillator remains perpendicular to the axis of theradiation beam when the radiation source is controlled to move aroundthe bore.

Item 18: The system of any one of the preceding items, wherein the boreis part of an MRI-guided radiotherapy system.

Item 19: The system of any one of the preceding items, furthercomprising a support structure configured to be mounted to the bore, andthe one or more cameras are fixed to the support structure.

Item 20: The system of any one of the preceding items, wherein the oneor more cameras are oriented to view respective portions of thescintillator adjacent to the one or more of cameras.

Item 21: The system of any one of the preceding items, wherein thescintillator is also mounted to the support structure.

Item 22: The system of any one of the preceding items, furthercomprising a non-transitory, machine-readable medium storinginstructions which, when executed by at least one programmableprocessor, cause operations comprising: applying an edge detectionalgorithm to a radiation pattern present in the images, the edgedetection algorithm determining at least one edge of the radiationpattern corresponding to a leaf of a multi-leaf collimator; anddetermining a leaf position based at least on a location of thedetermined edge.

Item 23: The system of any one of the preceding items, the operationsfurther comprising comparing the leaf position during delivery of theradiation beam with a planned leaf position, the comparing utilized inradiation therapy quality assurance.

Item 24: The system of any one of the preceding items, the operationsfurther comprising calculating a fluence map based at least on the leafposition and beam output data obtained from the radiation therapysystem.

Item 25: The system of any one of the preceding items, the operationsfurther comprising calculating a dose at a target location based atleast on the fluence map and a patient image obtained from an imagingsystem.

Item 26: The system of any one of the preceding items, wherein the doseis a three-dimensional dose delivered at the target location.

Item 27: A system or computer program product of any of the precedingitems, comprising a non-transitory, machine-readable medium storinginstructions which, when executed by at least one programmableprocessor, cause the at least one programmable processor to performoperations comprising: controlling a camera to acquire images of lightemitted by a scintillator during delivery of a radiation beam, thescintillator and the camera fixed to a support structure such that whenthe support structure is mounted to a radiation delivery system, thatthe scintillator is not perpendicular to an axis of the radiation beam,the images capturing at least a portion of a shape of a radiation fieldgenerated by the radiation delivery system that includes a radiationsource configured to deliver the radiation beam.

Item 28: The system or computer program product of any one of thepreceding items, the operations further comprising: applying an edgedetection algorithm to a radiation pattern present in the images, theedge detection algorithm determining at least one edge of the radiationpattern corresponding to a leaf of a multi-leaf collimator; anddetermining a leaf position based at least on a location of thedetermined edge.

Item 29: The system or computer program product of any one of thepreceding items, the operations further comprising comparing the leafposition during delivery of the radiation beam with a planned leafposition, the comparing utilized in radiation therapy quality assurance.

Item 30: The system or computer program product of any one of thepreceding items, the operations further comprising calculating a fluencemap based at least on the leaf position and beam output data obtainedfrom the radiation therapy system.

Item 31: The system or computer program product of any one of thepreceding items, the operations further comprising calculating a dose ata target location based at least on the fluence map and a patient imageobtained from an imaging system.

Item 32: The system or computer program product of any one of thepreceding items, wherein the dose is a three-dimensional dose deliveredat the target location.

The present disclosure contemplates that the calculations disclosed inthe embodiments herein may be performed in a number of ways, applyingthe same concepts taught herein, and that such calculations areequivalent to the embodiments disclosed.

One or more aspects or features of the subject matter described hereincan be realized in digital electronic circuitry, integrated circuitry,specially designed application specific integrated circuits (ASICs),field programmable gate arrays (FPGAs) computer hardware, firmware,software, and/or combinations thereof. These various aspects or featurescan include implementation in one or more computer programs that areexecutable and/or interpretable on a programmable system including atleast one programmable processor, which can be special or generalpurpose, coupled to receive data and instructions from, and to transmitdata and instructions to, a storage system, at least one input device,and at least one output device. The programmable system or computingsystem may include clients and servers. A client and server aregenerally remote from each other and typically interact through acommunication network. The relationship of client and server arises byvirtue of computer programs running on the respective computers andhaving a client-server relationship to each other.

These computer programs, which can also be referred to programs,software, software applications, applications, components, or code,include machine instructions for a programmable processor, and can beimplemented in a high-level procedural language, an object-orientedprogramming language, a functional programming language, a logicalprogramming language, and/or in assembly/machine language. As usedherein, the term “machine-readable medium” (or “computer readablemedium”) refers to any computer program product, apparatus and/ordevice, such as for example magnetic discs, optical disks, memory, andProgrammable Logic Devices (PLDs), used to provide machine instructionsand/or data to a programmable processor, including a machine-readablemedium that receives machine instructions as a machine-readable signal.The term “machine-readable signal” (or “computer readable signal”)refers to any signal used to provide machine instructions and/or data toa programmable processor. The machine-readable medium can store suchmachine instructions non-transitorily, such as for example as would anon-transient solid-state memory or a magnetic hard drive or anyequivalent storage medium. The machine-readable medium can alternativelyor additionally store such machine instructions in a transient manner,such as for example as would a processor cache or other random accessmemory associated with one or more physical processor cores.

To provide for interaction with a user, one or more aspects or featuresof the subject matter described herein can be implemented on a computerhaving a display device, such as for example a cathode ray tube (CRT) ora liquid crystal display (LCD) or a light emitting diode (LED) monitorfor displaying information to the user and a keyboard and a pointingdevice, such as for example a mouse or a trackball, by which the usermay provide input to the computer. Other kinds of devices can be used toprovide for interaction with a user as well. For example, feedbackprovided to the user can be any form of sensory feedback, such as forexample visual feedback, auditory feedback, or tactile feedback; andinput from the user may be received in any form, including, but notlimited to, acoustic, speech, or tactile input. Other possible inputdevices include, but are not limited to, touch screens or othertouch-sensitive devices such as single or multi-point resistive orcapacitive trackpads, voice recognition hardware and software, opticalscanners, optical pointers, digital image capture devices and associatedinterpretation software, and the like.

In the descriptions above and in the claims, phrases such as “at leastone of” or “one or more of” may occur followed by a conjunctive list ofelements or features. The term “and/or” may also occur in a list of twoor more elements or features. Unless otherwise implicitly or explicitlycontradicted by the context in which it used, such a phrase is intendedto mean any of the listed elements or features individually or any ofthe recited elements or features in combination with any of the otherrecited elements or features. For example, the phrases “at least one ofA and B;” “one or more of A and B;” and “A and/or B” are each intendedto mean “A alone, B alone, or A and B together.” A similarinterpretation is also intended for lists including three or more items.For example, the phrases “at least one of A, B, and C;” “one or more ofA, B, and C;” and “A, B, and/or C” are each intended to mean “A alone, Balone, C alone, A and B together, A and C together, B and C together, orA and B and C together.” Use of the term “based on,” above and in theclaims is intended to mean, “based at least in part on,” such that anunrecited feature or element is also permissible.

The subject matter described herein can be embodied in systems,apparatus, methods, computer programs and/or articles depending on thedesired configuration. Any methods or the logic flows depicted in theaccompanying figures and/or described herein do not necessarily requirethe particular order shown, or sequential order, to achieve desirableresults. The implementations set forth in the foregoing description donot represent all implementations consistent with the subject matterdescribed herein. Instead, they are merely some examples consistent withaspects related to the described subject matter. Although a fewvariations have been described in detail above, other modifications oradditions are possible. In particular, further features and/orvariations can be provided in addition to those set forth herein. Theimplementations described above can be directed to various combinationsand subcombinations of the disclosed features and/or combinations andsubcombinations of further features noted above. Furthermore, abovedescribed advantages are not intended to limit the application of anyissued claims to processes and structures accomplishing any or all ofthe advantages.

Additionally, section headings shall not limit or characterize theinvention(s) set out in any claims that may issue from this disclosure.Further, the description of a technology in the “Background” is not tobe construed as an admission that technology is prior art to anyinvention(s) in this disclosure. Neither is the “Summary” to beconsidered as a characterization of the invention(s) set forth in issuedclaims. Furthermore, any reference to this disclosure in general or useof the word “invention” in the singular is not intended to imply anylimitation on the scope of the claims set forth below. Multipleinventions may be set forth according to the limitations of the multipleclaims issuing from this disclosure, and such claims accordingly definethe invention(s), and their equivalents, that are protected thereby.

What is claimed is:
 1. A system for determining at least a portion ofthe shape of a radiation field generated by a radiation delivery systemthat includes a radiation source configured to deliver a radiation beam,system comprising: a scintillator mounted to the radiation deliverysystem such that the scintillator substantially follows a contour of abore of the radiation delivery system; and one or more camerasconfigured to acquire images of light emitted by the scintillator duringdelivery of the radiation beam.
 2. The system of claim 1, wherein thescintillator is a curved sheet of scintillating material.
 3. The systemof claim 1, wherein the scintillator comprises a plurality of planarsheets of scintillating material.
 4. The system of claim 1, wherein atleast one portion of the scintillator remains perpendicular to the axisof the radiation beam when the radiation source is controlled to movearound the bore.
 5. The system of claim 1, wherein the scintillator isat a larger radial distance than an internal surface of the bore.
 6. Thesystem of claim 1, wherein the scintillator is at a smaller radialdistance than an internal surface of the bore.
 7. The system of claim 1,wherein the bore is part of an MRI-guided radiotherapy system.
 8. Thesystem of claim 1, wherein the one or more cameras are configured to bemounted at an angle of greater than 0 and less than 10 degrees relativeto the scintillator.
 9. The system of claim 1, further comprising asupport structure configured to be mounted to the bore, and the one ormore cameras are fixed to the support structure.
 10. The system of claim9, wherein the one or more cameras are oriented to view respectiveportions of the scintillator adjacent to the one or more cameras. 11.The system of claim 9, wherein the scintillator is also mounted to thesupport structure.
 12. The system of claim 1, further comprising anon-transitory, machine-readable medium storing instructions which, whenexecuted by at least one programmable processor, cause operationscomprising: applying an edge detection algorithm to a radiation patternpresent in the images, the edge detection algorithm determining at leastone edge of the radiation pattern corresponding to a leaf of amulti-leaf collimator; and determining a leaf position based at least ona location of the determined edge.
 13. The system of claim 12, theoperations further comprising comparing the leaf position duringdelivery of the radiation beam with a planned leaf position, thecomparing utilized in radiation therapy quality assurance.
 14. Thesystem of claim 12, the operations further comprising calculating afluence map based at least on the leaf position and beam output dataobtained from the radiation therapy system.
 15. The system of claim 14,the operations further comprising calculating a dose at a targetlocation based at least on the fluence map and a patient image obtainedfrom an imaging system.
 16. A computer program product comprising anon-transitory, machine-readable medium storing instructions which, whenexecuted by at least one programmable processor, cause the at least oneprogrammable processor to perform operations comprising: controlling oneor more cameras to acquire images of light emitted by a scintillatorduring delivery of a radiation beam, the scintillator mounted to aradiation delivery system such that the scintillator substantiallyfollows a contour of a bore of the radiation delivery system.
 17. Thecomputer program product of claim 16, the operations further comprising:applying an edge detection algorithm to a radiation pattern present inthe images, the edge detection algorithm determining at least one edgeof the radiation pattern corresponding to a leaf of a multi-leafcollimator; and determining a leaf position based at least on a locationof the determined edge.
 18. The computer program product of claim 17,the operations further comprising comparing the leaf position duringdelivery of the radiation beam with a planned leaf position, thecomparing utilized in radiation therapy quality assurance.
 19. Thecomputer program product of claim 18, the operations further comprisingcalculating a fluence map based at least on the leaf position and beamoutput data obtained from the radiation therapy system.
 20. The computerprogram product of claim 16, the operations further comprisingcalculating a dose at a target location based at least on the fluencemap and a patient image obtained from an imaging system.
 21. Thecomputer program product of claim 16, wherein the images are acquiredwith the one or more cameras which are mounted at an angle of greaterthan 0 and less than 10 degrees relative to the scintillator.